Portable external grinder



A. MGDIARMID PORTABLE EXTERNAL GRINDER March 29, 1949.

2 Sheets-Sheet 1 Filed July 25, 1945 gjjjjj ij 1 lllm , INVENIOR.

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PORTABLE EXTERNAL GRINDER Filed July 25, 1945 2 SheetsSheet 2 INVENTOR. I716! ander ///c fi/arm d ggw #torney Patented Mar. 29, 1949 Ulirl STATS B T YET.

OFEQE PORTABLE EXTERNAL GRINDER Virginia Application July 23, 1945, Serial No. 606,556

(Ci. 5124l) 2 Claims.

The present invention relates to thread grinders and has among its objects a device easily transportable and capable of use in service operations on certain threads without the necessity of dismantling the machine being serviced.

In the shipment of airplane engines, these, of course, are transported with-out propeller and it often happens that the accurately threaded crankshaft ends become somewhat damaged in transit. Obviously, it is impracticable to remove the crankshaft for the purpose of repairing such threads and heretofore such repairs have had to be moreor less of a makeshift.

Another object of the invention, therefore, is a thread grinder capable of being mounted on the assembled engine and of re-grinding the threads without removing any engine parts, and, while the following description refers to engines and crankshafts, it is obvious that the device may be adapted to other uses with only minor modification, and such other uses are not hereby disclaimed.

In the drawings:

Fig. 1 is a sectional view through the device.

Fig. 2 is a top plan view with parts broken away.

Fig. 3 is a sectional View of the mandrel as in the line 33 of Fig. 1.

Fi 4 is a side elevation on a smaller scale.

The device consists of a body member 1!! provided with a recess I i approximately half way of its length, and having coaxial bores in the two end portions. Carried on the lower end of the body is a hand wheel I2, and on th upper portion of the body is a suitable plate i3, which plate extends laterally and is provided with ways in which is mounted the laterally movable member Hi, itself provided with suitable ways in which a slide member 16 is arranged to slide 1ongitudinally of the body It]. The slide I6 is movable by and held in adjusted position by a suitable screw 70.

Mounted on the slide is a post I! carrying a member I8, which in one portion is provided with a suitable bearing is for a rotatable shaft 20, :upon which, at its lower end, is a suitable grinding wheel 2!. The wheel 21 is opposite and extends into the recess II, and, as shown in Fig. 4, may be provided with a suitable guard 21A.

At its upper end, the shaft is provided with a small pulley 22. The member 58 also carries an electric motor 25 provided with a pulley 26 for driving the pulley 22 by means Of a suitable belt 21.

Fixed within the upper bore in body It] is a sleeve 36, the sleeve being held in position by means of a suitable screw 3|. This sleeve is the female member or nut for a lead screw 35, the male member being shown at 36 as extending through the sleeve 39 into the recess II and having its lower end beveled or tapered as indicated at 3?.

Within the member 36 is fitted a hollowmandrel 38, the mandrel extending beyond the recess ii and well into the lower bore in body [0, and within the hollow mandrel 38 is a rod '39 which extends to the lower end of the mandrel. This rod is provided near its lower end with a plurality of flat sloping cam faces 49.

In Fig. 3 the rod 39 is shown to have three of such cam surfaces and to coact with three plugs 4!, each provided with a correspondingly sloping face and extending through the wall of the mandrel. Obviously when the rod is moved lengthwise of the mandrel, the plugs M will be moved radially inwardly or outwardly.

Fitted into the bore in the lower portion of the body is a sleeve 50 carrying a small plug member 5! adapted to be fixed in adjusted position by means of a set screw 52.

Since the device is intended primarily for grinding the threads on the end of a crankshaft for airplane engines, such a crankshaft end is indicated at N! in Figs. 1 and 4. Such crankshaft ends are splined for a portion of their extending ends and provided at the extreme end with a reduced threaded portion as at El which is the thread to be ground. The sleeve 50 is ground on the outside to fit accurately in the lower bore in the body ill, and on the inside to fit the tops of the splines on the crankshaft, while the plug 5| is provided with a flattened inner end which fits between splines and fixes the sleeve 50 and crankshaft against relative rotation.

Since such cranlzshafts are usually hollow, the mandrel 38 is made s'uficiently long to extend well down into such hollow shaft and is fixed therein by means of the rod 39 upon the extended end of which is a suitable nut 39A by means of which the rod is drawn up, to thereby move the plugs 4| outwardly.

Such crankshafts also are usually provided with a bevel at the end of the bore and the beveled end 3? of the member 36 is adapted to fit in such beveled end. This member 35 is fixed to the mandrel 38 by means of a cap 36A slipped over the extended end of rod 39 and held tightly against the member 36 by means of a nut 363.

It will be noted from Fig. 1 that with the parts in position to be operated, the stationary elements are the crankshaft 60, sleeve 50, mandrel 38 and lead screw member 36. The rest of the assembly is supported on and may be rotated around the lead screw 35. This latter, will, of course, correspond to the threads upon the crankshaft.

When the sleeve 50 has been placed over the end of the crankshaft and the body i carrying the parts described lowered over the sleeve until the end of the mandrel enters the opening in the crankshaft, the mandrel is then tightened and the member 36 fixed against movement thereon.

With the parts rotated so that the sleeve 38) is in its upper position, the grinding wheel H is adjusted to enter the thread 6i properly and at the proper point by means of the adjusting screw 10 for the slide H5. The motor then being started, the assembly is rotated by means of the hand wheel 12 so that the lead screw 35 causes the wheel 2| to follow the thread down to its root.

As shown in Fig. 4, the device may be provided with a suitable bail '15 by means of which it may be supported or moved by means of a suitable hoist indicated by the hook 16.

Further, since the Weight distribution of the device is non symmetrical, it is desirable to provide a counterweighted arm Tl extending'laterally opposite the motor 25 and adjacent parts so as to substantially counterbalance these.

Now having described the invention and the preferred embodiment thereof, it is to be understood that said invention is to be limited, not to the specific details herein set forth, but only by the scope of the claims which follow.

I claim:

1. A device of the character described consisting of an elongated body portion provided with a recess in its central portion and having coaxial bores opening to said recess, a guide sleeve rotatably mounted in one of said bores, a lead nut fixed in the other of said bores, a hollow member provided with a male lead screw coacting therewith, a mandrel within said male screw carrying member, means for fixing a workpiece within said sleeve and to said mandrel with a portion extending into said recess, means for fixing said mandrel to said male lead screw, and a thread grinding wheel carried by said body portion and extending into said recess into contact with said workpiece.

2. In a device for grinding threads on the end of a hollow shaft, a mandrel adapted to be fixed in said shaft, a sleeve fitted around said mandrel and having lead screw threads on its periphery, a second sleeve fitted around the first sleeve and provided on its inner periphery with threads adapted to cooperate with the first threads, a body member in which said second sleeve is fixed, said body member carrying a thread grinding wheel and means for rotating the same, means for fixing said mandrel in said shaft end and means for fixing said first sleeve to said mandrel and to said shaft end.

ALEXANDER MCDIARMID.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 764,341 Bond July 5, 1904 1,326,091 Porter Dec. 23, 1919 1,412,778 Cumner et al Apr. 11, 1922 1,818,288 Walker Aug. 11, 1931 

